Jester receiving king's summons? (4)
I believe the answer is:
writ
'summons?' is the definition.
(summons is a kind of writ)
'jester receiving king's' is the wordplay.
'jester' becomes 'wit' (both can mean a comical person).
'receiving' is an insertion indicator.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'wit' enclosing 'r' is 'WRIT'.
(Other definitions for writ that I've seen before include "What scribe did" , "court paper" , "Legal document (usually issued)" , "Legal document of command" , "It may be served" .)